Mostly working, labels don't go on their paths.

project.clj

@@ -3,7 +3,8 @@
                  [generateme/fastmath "2.4.0"]
                  [hiccup "2.0.0-RC3"]
                  [javax.xml.bind/jaxb-api "2.4.0-b180830.0359"]
-                 [org.clojure/clojure "1.8.0"]
+                 [org.clojure/clojure "1.11.3"]
+                 [org.clojure/data.xml "0.0.8"]
                 ;;  [org.clojure/clojurescript "1.9.229"]
                 ;;  [org.omcljs/om "1.0.0-beta1"]
                 ;;  [reagent "0.6.0"]

resources/public/sample-data.edn

@@ -1,40 +1,125 @@
 {:id "ge2024"
  :label "UK General Election 2024"
+ :colour "white"
  :children [{:id "no-show"
              :label "Did not vote"
-             :magnitude 18365357}
+             :quantity 18365357}
             {:id "voted"
              :label "Voted"
-             :children [{:id "reform"
+             :children [{:id "labour"
-                         :label "Reform UK Ltd."
-                         :magnitude 4091549}
-                        {:id "greenew"
-                         :label "Green Party of England and Wales"
-                         :magnitude 1939502}
-                        {:id "pc"
-                         :label "Plaid Cymru"
-                         :magnitude 194811}
-                        {:id "sf"
-                         :label "Sinn Féin"
-                         :magnitude 210891}
-                        {:id "ld"
-                         :label "Liberal Democrats"
-                         :magnitude 3499933}
-                        {:id "labour"
                          :label "Labour"
-                         :magnitude 9712011}
+                         :colour "red"
-                        {:id "apni"
+                         :quantity 9712011
-                         :label "Alliance Party"
+                         :children [{:id "negative"
-                         :magnitude 117191}
+                                     :colour "gray"
-                        {:id "sdlp"
+                                     :children [{:id "anti-tory"
-                         :label "Social Democratic and Labour Party"
+                                                 :label "To get the Tories out"
-                         :magnitude 86861}
+                                                 :colour "#424242"
-                        {:id "dup"
+                                                 :quantity 4658234}
-                         :label "Democratic Unionist Party"
+                                                {:id "change"
-                         :magnitude 172058}
+                                                 :label "The country needs a change"
-                        {:id "snp"
+                                                 :colour "#424242"
-                         :label "Scottish National Party"
+                                                 :quantity 1261605}
-                         :magnitude 708759}
+                                                {:id "nhs"
+                                                 :label "To support the NHS"
+                                                 :colour "#424242"
+                                                 :quantity 388186}
+                                                {:id "alternative"
+                                                 :label "The best alternative"
+                                                 :quantity 388186}
+                                                {:id "anti-sunak"
+                                                 :label "Rishi Sunak"
+                                                 :colour "#424242"
+                                                 :quantity 97047}
+                                                {:id "anti-snp"
+                                                 :label "To oust the SNP"
+                                                 :colour "#424242"
+                                                 :quantity 97047}]}
+                                    {:id "other"
+                                     :colour "maroon"
+                                     :quantity 291140}
+                                    {:id "positive"
+                                     :colour "red"
+                                     :children [{:id "policies"
+                                                 :label "I agree with their policies"
+                                                 :colour "#d32f2f"
+                                                 :quantity 485233}
+                                                {:id "mp"
+                                                 :label "Like my MP"
+                                                 :colour "#d32f2f"
+                                                 :quantity 194093}
+                                                {:id "fairer"
+                                                 :label "For a fairer society"
+                                                 :colour "#d32f2f"
+                                                 :quantity 194093}
+                                                {:id "habit"
+                                                 :label "I always vote Labour"
+                                                 :colour "#d32f2f"
+                                                 :quantity 194093}
+                                                {:id "honesty"
+                                                 :quantity 194093}
+                                                {:id "caop"
+                                                 :label "Care about ordinary people"
+                                                 :colour "#d32f2f"
+                                                 :quantity 97047}
+                                                {:id "fwc"
+                                                 :label "For the working class"
+                                                 :colour "#d32f2f"
+                                                 :quantity 97047}
+                                                {:id "cl"
+                                                 :label "Address the cost of living"
+                                                 :colour "#d32f2f"
+                                                 :quantity 97047}
+                                                {:id "stability"
+                                                 :label "Economic stability"
+                                                 :colour "#d32f2f"
+                                                 :quantity 97047}
+                                                {:id "pro-starmer"
+                                                 :label "Keir Starmer"
+                                                 :colour "#d32f2f"
+                                                 :quantity 97047}
+                                                {:id "services"
+                                                 :label "For better public services"
+                                                 :colour "#d32f2f"
+                                                 :quantity 97047}]}]}
                         {:id "con"
                          :label "Conservative"
-                         :magnitude 6814469}]}]}
+                         :colour "blue"
+                         :quantity 6814469}
+                        {:id "ld"
+                         :label "Liberal Democrats"
+                         :colour "gold"
+                         :quantity 3499933}
+                        {:id "snp"
+                         :label "Scottish National Party"
+                         :colour "yellow"
+                         :quantity 708759}
+                        {:id "sf"
+                         :label "Sinn Féin"
+                         :quantity 210891}
+                        {:id "independents"
+                         :label "independents"
+                         :colour "silver"
+                         :quantity 564243}
+                        {:id "reform"
+                         :label "Reform UK Ltd."
+                         :colour "cyan"
+                         :quantity 4091549}
+                        {:id "dup"
+                         :label "Democratic Unionist Party"
+                         :quantity 172058}
+                        {:id "greenew"
+                         :label "Green Party of England and Wales"
+                         :colour "green"
+                         :quantity 1939502}
+                        {:id "pc"
+                         :label "Plaid Cymru"
+                         :colour "#005b54"
+                         :quantity 194811}
+                        {:id "apni"
+                         :label "Alliance Party"
+                         :colour "#f6cb2f"
+                         :quantity 117191}
+                        {:id "sdlp"
+                         :label "Social Democratic and Labour Party"
+                         :quantity 86861}]}]}

src/clj/rsvggraph/core.clj

@@ -1 +1,92 @@
-(ns rsvggraph.core)
+(ns rsvggraph.core
+  (:require [clojure.math :refer [cos PI sin]]
+            [clojure.string :refer [join replace]]
+            [clojure.xml :refer [emit]]
+            [fastmath.core :refer [pow]]
+            [hiccup2.core :refer [html]]
+            [rsvggraph.data :refer [normalise]]))
+
+
+
+(defn polar-to-cartesian
+  "Return, as a map with keys :x. :y, the cartesian coordinates at the point
+   `radius` distance at `theta` (degrees) angle from a point at
+   cartesian coordinates `cx`, `cy`."
+  [cx cy radius theta]
+  (let
+   [in-radians (/ (* (- theta 90) PI) 180.0)]
+    {:x (+ cx (* radius (cos in-radians)))
+     :y (+ cy (* radius (sin in-radians)))}))
+
+(defn describe-arc
+  "Return as a string an SVG path definition describing an arc centred
+   at `cx`, cy` starting at `start-angle` and ending at `end-angle` (both
+   angles in degrees)."
+  [cx cy radius start-angle end-angle]
+  (let
+   [start (polar-to-cartesian cx cy radius start-angle)
+    end (polar-to-cartesian cx cy radius end-angle)
+    large-arc? (if (<= (- end-angle start-angle) 180) 0 1)
+    sweep (if (> end-angle start-angle) 1 0)]
+    (join " " ["M" (:x start) (:y start) "A" radius radius 0 large-arc? sweep (:x end) (:y end)])))
+
+(defn draw-segment
+  [datum diameter]
+  (let [r' (/ diameter 2)
+        thickness (/ r' (:ring datum));; (/ 1 (pow 3 (:ring datum)))
+        radius (- r' (/ thickness 2))
+        start-angle (* (:left datum) 360)
+        end-angle (* (:right datum) 360)
+        id (str (:id datum) "-segment")
+        path-data (describe-arc r' r' radius start-angle end-angle)]
+;;    (println (format "Id: %s; radius: %s; start: %s; end: %s; thickness %s" id radius start-angle end-angle thickness))
+    [:g {:id (str id "group")}
+     [:path {:class "rsvggraph-segment"
+             :id id
+             :style {:fill "none"
+                     :stroke (:colour datum)
+                     :stroke-width thickness}
+             :d path-data}]
+     [:text [:textPath {:href (str "#" id)
+                        :path path-data} (:label datum)]]]))
+
+(defn flatten-data
+  [data]
+  (cond (empty? (:children data)) data
+        :else (flatten (cons (dissoc data :children) (map flatten-data (:children data))))))
+
+(def ^:dynamic *background* "white")
+
+(def ^:dynamic *foreground* "black")
+
+(defn data->svg
+  [data diameter]
+  (let [data' (normalise data)]
+    [:svg {:xmlSpace "preserve"
+           :overflow "visible"
+           :viewBox (join " " [0 0 diameter diameter])
+           :width (str diameter "px")
+           :height (str diameter "px")
+           :y "0px"
+           :x "0px"
+           :version "1.1"
+           :id (:id data')
+           :class (str "rsvggraph-graph")
+           :xmlns "http://www.w3.org/2000/svg"}
+     [:circle {:id (str (:id data') "-background") :cx (/ diameter 2) :cy (/ diameter 2) :r (/ diameter 2) :style {:fill "white"}}]
+     [:text
+      {:text-anchor "middle"
+       :x (/ diameter 2)
+       :y (/ diameter 2)
+       :width (/ diameter 4)
+       :id (str (:id data') "-title")
+       :class "rsvggraph-value"} [:tspan (:label data) ": " (:quantity data)]]
+     (map #(draw-segment % diameter) (flatten-data data))]))
+
+(defn data->svg-file
+  [data diameter path]
+  (emit (data->svg data diameter)))
+
+(defn data->html-file
+  [data diameter path]
+  (spit path (join "\n" ["<?xml version='1.0' encoding='UTF-8'?>" (replace (html (data->svg data diameter)) #"\> *\<" ">\n<")])))

src/clj/rsvggraph/data.clj

@@ -1,29 +1,89 @@
 (ns rsvggraph.data
-  "Normalise data for use in generating radial graphs."
+  "Normalise data for use in generating radial graphs. A lot of the things
-  (:require [clojure2d.color :refer [gradient]]))
+   I want to do here, especially with colour, are not readily portable between
+   clojure and clojurescript, so this is Clojure only for now."
+  (:require [clojure2d.color :refer [format-hex gradient]]
+            [fastmath.core :refer [pow]]))
 
 
-(def ;; ^:dynamic 
+(def ^:dynamic *gradient*
-  *gradient*
   "The gradient to use to automatically assign pleasing colours to sectors, if
    no colours are defined in the data. Suitable gradients are defined 
    [here](https://clojure2d.github.io/clojure2d/docs/static/gradients/)."
   :rainbow2)
 
-(def children-fn
+(def ^:dynamic *children*
   "Basic (overridable) children function; assumes `data` is a map, and returns 
    the value of the `:children` key within that map."
   (memoize (fn [data]
              (:children data))))
 
-(def quantity-fn
+(def ^:dynamic *quantity*
   "Basic (overridable) children function; assumes `data` is a map. If the value
    of the `:children` key within that map is a sequence, sums the result of 
    mapping itself over that sequence. Otherwise, returns the value of the 
    `:quantity` key, if present and a number, or `1` as a final default."
   (memoize (fn [data]
-             (let [c (children-fn data)
+             (let [c (*children* data)
                    q (:quantity data)]
-               (cond (coll? c) (reduce + 0 (map quantity-fn c))
+               (cond (number? q) q
-                     (number? q) q
+                     (coll? c) (reduce + 0 (map *quantity* c)) 
-                     :else 1)))))
+                     :else 1)))))
+
+(def ^:dynamic *colour*
+  "Return, as a hex string acceptable to HTML and CSS, the appropriate colour
+   for this `datum` having this `central-quantity-fraction` as the centre of
+   its position in the arc."
+  (fn [data central-quantity-fraction]
+    (let [col (:colour data)
+          grad (gradient *gradient*)]
+      (cond
+        col col
+        (number? data) (format-hex (grad data))
+        (number? central-quantity-fraction) (format-hex (grad central-quantity-fraction))
+        :else "gray"))))
+
+(def proportion
+  (memoize
+   (fn [data total]
+     (double (/ (*quantity* data) total)))))
+
+(defn normalise
+  ([data]
+   (normalise data 1 (*quantity* data) 0))
+  ([data ring total left]
+   (let [id (or (:id data)
+                (keyword (gensym (or (:title data) "datum"))))
+         q (*quantity* data)
+         p (proportion data total)
+         color (*colour* data (+ left (/ p 2)))]
+     (assoc data
+            :children
+            (when (:children data)
+              (loop [c (first (:children data))
+                     l left
+                     y (rest (:children data))
+                     v nil]
+                (let [r (+ l (proportion c total))
+                      c' (assoc
+                                (normalise c (inc ring) total l)
+                                :left l
+                                :right r)
+                      v' (cons c' v)]
+                  ;; (println (format "Label: %s: ring: %d; left: %f; right: %f; colour %s." 
+                                  ;;  (:label c') ring (double l) r color))
+                  (cond (empty? y) (vec v')
+                        :else
+                        (recur (first y)
+                               r
+                               (rest y)
+                               v')))))
+            :colour color
+            :id id
+            :inner-diameter (/ 1 (pow 3 ring))
+            :label (or (:label data) id)
+            :left 0
+            :proportion p
+            :quantity q
+            :right 1
+            :ring ring))))